It's a plotter like device to plot over a cardboard or a canvas

1. Painting machine
based on Hektor:
http://hektor.ch

2. Motivation
The need to print on an arbitrarily large format
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Vector graphics will be scaled up or down to fit
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the desired format
The system needs to be easy to carry around
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not heavy
–
not large
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if possible, autonomous (no PC attached)
–

3. Physics
L
(0,0)
2 2 2
a =x y
2 2 2
b = L− x   y
a
b
a­­
b­­
a­­ a++
b++ b­­
(x,y)
a++
b++

4. Software design
moveTo(x,y)
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starting from a previous point (x0,y0)
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Bresenham's line algorithm?
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both motors will run at once?
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Reverse equations:
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2 2 2
L a −b 2 2
x= y=   a −x 
2L

5. Non linearity
Linear steps create curves instead of straight
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lines
Steps Equivalent XY motion
4100 1600
4000
1400
3900
1200
3800
3700 1000
3600
800
3500
600
3400
3300
400
3200
200
3100
3000 0
0 500 1000 1500 2000 0 2000

6. Line drawing
Use Bresenham algorithm and then convert
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coordinates
Only needed when drawing lines
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If pen is up other choices are possible
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It works ok!!
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Problem: Both motors need to work in sync
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Unpredictable next step
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Not ramp up/down speed
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But painting works better at a fixed pen speed!!
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7. Samples

8. Motor detail